The present invention relates to soil sampling systems and, more particularly, to hollow-tubed soil samplers. A major objective of the present invention is to provide for enhanced collection of soil samples for chemical or physical analysis.
Contamination of soils is a major environmental concern. Toxic compounds can remain in the soil for years, and can seep into groundwater, causing serious environmental and health problems. Because contamination is often located many feet below the surface, identifying and treating contaminated soils can be problematic.
In a typical system for sampling for soil contamination, soil samples are collected at discrete levels. A hollow-stem auger powered by a large motor drill rig is typically used. The drilling rig can weigh as much as 30 tons, and is typically mounted on a large truck. The auger is typically about 8" in diameter. The outside has a spiral flighting that aids travel through the soil and that removes the waste dirt ("cuttings") from the borehole. During drilling, the hollow auger is plugged.
After the initial soil depth to be investigated is reached, and while the auger is in place in the ground, the plug is removed. Next, a hollow cylindrical drive sampler is inserted into the hole created by the auger. The drive sampler is driven, via a drive rod and hydraulic or pneumatic hammer, ahead of the lead auger into the soil to be sampled. Soil is forced into the hollow center of the drive sampler, which can contain stainless steel or brass sample sleeves. A large winch, usually attached to a mast about 20' tall, then engages the drive rod, and the drive rod, sampler, sleeves, and soil are removed, leaving an open hole. For the next sample, the auger drills to the next depth to be sampled, and the process is repeated.
In cases of chemical contamination, contaminated soil may be confined to thin soil layers, sometimes only an inch or two thick. The discrete sampling of many previous systems, often taken at intervals of several feet, can miss areas of contamination and yield false negative results.
Furthermore, where contamination is encountered, the cuttings created by the typical augering system and brought to the ground surface, are also often contaminated, and must be disposed of as hazardous waste. Such disposal is often difficult and very expensive, because the soil requires special handling and disposal.
Single-rod non-auger drilling systems are sometimes used to sample relatively shallow depths. Single-rod systems can often be driven by more compact drilling rigs, but they are associated with other problems. To retrieve the sampler from the soil, skin friction of the soil must be overcome, requiring a significant amount of pull. In addition, because the borehole is not continuously cased off, contaminants from upper levels often slough off and contaminate lower levels, leading to false positive readings.
The drilling rig and winch in the typical prior art system can often harm the environment around the area to be tested. As described above, the entire system can be over 20' tall, weigh 30 tons, and be mounted on a truck 20' long. A rig in place can disrupt traffic. Landscaping around the area to be tested can be destroyed. If the area to be tested is under an existing structure, roofs or walls may have to be removed. Providing access for the equipment can also be destructive, time-consuming, and expensive.
What is needed is a soil sampling system that is compact and efficient, that allows for continuous, accurate soil samples to be collected, and that minimizes the amount of cuttings created during sampling.